Visual field testing is an important tool in the field of ophthalmology. It is currently the only test approved by the Food and Drug Administration for Glaucoma monitoring. Conventional visual field testing can take 10-30 minutes vs. 10-30 seconds for optical coherence tomography (OCT) or fundus imaging. One major reason for this length is due to inaccuracies in the conventional testing techniques. The Humphrey Visual Field Analyzer is one such tool currently available for performing a visual field test.
Accurate visual field testing is essential for tracking the progression of many neurological diseases including Glaucoma. The test involves asking a patient to direct their gaze on a fixation target while presenting stimuli to different parts of the retina (i.e., different parts of their field of view) and recording acknowledgement responses of the patient in the form of seen/not seen as registered by pushing a button. Knowing the gaze direction of the patient is important in order to identify which portion of the retina is being stimulated by a particular visual stimulus. The Humphrey Visual Field Analyzer operates in this manner.
However, the visual field data is often unreliable, especially for the target population of elderly whose vision is more often affected by Glaucoma. This unreliability stems from the patient's gaze direction drifting away from the fixation target while the visual stimuli are presented. Current tests attempt to ameliorate this problem by performing a gross gaze tracking of the pupil and reject responses when it is determined the user's gaze has drifted off the fixation target. Unfortunately, conventional gaze tracking based upon the pupil is only accurate to within a few degrees, which is not sufficiently accurate to identify with high precision when the user's gaze has drifted away from the fixation target. Repeating a presentation sequence of visual stimuli can improve the accuracy of visual field testing, but does so at the expense of prolonging the test. However, prolonging the test by repeating presentation sequences also has its limits in practice, as the patient's eyes begin to fatigue and their ability to maintain fixation on a fixation target reduces, thereby degrading the test results and increasing the number of rejected responses.